1. Field of the Invention
The present invention relates an optical disk recording apparatus, a laser diode driving apparatus and a recording signal generating apparatus for adjusting the recording signal to drive the laser diode and the timing of the laser light emission at the time of recording.
2. Description of the Related Art
The write strategy signal requires a very high timing accuracy, and a timing shift, if any, makes it impossible to obtain a predetermined write strategy, thereby directly deteriorating the recording quality. Actually, the timing of the write strategy signal is liable to be affected by the manufacturing variations of a circuit on the signal line, a change in an environmental factor such as temperature or a change in the electrical conditions of the signal transmission line, and the timing shift between signals is not same. In designing the optical disk recording apparatus, therefore, a great problem to be solved is how to maintain the timing accuracy of the write strategy signal in steady state within a tolerable range.
To cope with this problem, in the prior art, a variable delay circuit is inserted in a digital signal processing circuit including a write strategy generating circuit, and the delay time of the variable delay circuit is set in such a manner as to correct the mutual timing shift of the write strategy signals thereby to eliminate the timing shift at the time of designing the optical disk recording apparatus.
FIG. 5 shows an example of circuit blocks in which a digital signal processing circuit including the conventional write strategy generating circuit has a variable delay circuit, and the delay time of the variable delay circuit is set in such a manner as to correct the timing shift of the write strategy signals at the time of designing the device thereby to eliminate the timing shift.
The signal generated by a recording strategy generating circuit (not shown) in a recording signal processing circuit 8 is input to a variable delay circuit 82. The signal propagation delay time of the variable delay circuit 82 can be set by a system control signal 17 through a register circuit 80. The output of the variable delay circuit 82 is input to an IF circuit 84. The IF circuit 84 converts the signal level in the recording signal processing circuit 8 to the level of a recording signal 19 and outputs the recording signal 19. The recording signal 19 is transmitted through a printed circuit board, a flexible printed circuit board, a circuit board on an optical pickup, connectors used to connect these circuit boards to each other, an input interface circuit for a laser drive LSI and a laser drive current switch. The signal propagation delay time in this signal transmission path is generally varied between the paths a, b and c of the recording signal 19 depending on the difference of the signal path length and the delay time of the circuit.
The conventional techniques are described in JP-A-2001-202625 and JP-A-2004-152335.